Results from a 20 year study on monkeys and their diets show that eating fewer calories can help you live longer. Animals with a restricted diet of 30% were shown to outlive those that were given the freedom to eat what when and how much they wanted. The monkeys also had improved chances of avoiding age related diseases, cancer, diabetes and brain atrophy.

In terms of overall animal health, Weindruch notes, the restricted diet leads to longer lifespan and improved quality of life in old age. "There is a major effect of caloric restriction in increasing survival if you look at deaths due to the diseases of aging," he says.

The incidence of cancerous tumors and cardiovascular disease in animals on a restricted diet was less than half that seen in animals permitted to eat freely. Remarkably, while diabetes or impaired glucose regulation is common in monkeys that can eat all they want, it has yet to be observed in any animal on a restricted diet. "So far, we've seen the complete prevention of diabetes," says Weindruch.